A couple of years ago there was a study that posited that a genetic variant was responsible for the fact that for some people cilantro (known as coriander leaves in some countries) is delicious and for others it tastes extremely bad. Many of the people in the latter group characterize the bad flavor as something like "soap." The study has been making the rounds again lately with this article.
The "soap tasting" variant is AA on rs72921001.
Turns out I'm AA there (if you have 23andme you can get your genotype via this blog post). And I love cilantro.
Do I secretly desire to slather my mouth with soap? Well what is the flavor of soap anyway? Plain soap really has no flavor or smell, usually scents are added to the soap. And they vary from place to place and culture to culture.
It's interesting because a lot of Europeans who have tried American root beer say it has a flavor like soap or toothpaste. They didn't grow up with it like most Americans did. Similarly, the French have these amazing violet and rose candies that many Americans claim have flavors of perfume. We largely didn't grow up eating these thing kind of flavors and therefore probably did only encounter them in perfume or other beauty products.
I would counter that it's not that cilantro has a soapy flavor to some people, it's simply that it has a strong flavor that only some people can detect very strongly and some of these people don't like that.
Personally it doesn't surprise me that I'd like something that some people perceive as tasting like soap because I like a lot of stuff that people have told me tastes like soap to them. Like mastic, which is a tree resin used in some foods common in Greece, Turkey, and Lebanon. When Jeni's Ice Cream did the cedar and fir flavored ice creams last winter, many people said they tasted like Pinesol, but I loved them. I also really enjoy some bitter digestifs that many people say are medicinal tasting such as Underberg.
So yeah, how you perceive cilantro is genetic, but also colored by culture and personal preference.